In a sand casting process for an aluminum internal combustion engine block, an expendable mold package is assembled from a plurality of resin-bonded sand cores that define the internal and external surfaces of the engine block. Typically, each of the sand cores is formed by blowing resin-coated foundry sand into a core box and curing it therein. Cast-in-place bore liners are often used in such castings.
Typically, in the manufacture of an aluminum engine block with cast-in-place bore liners, the mold assembly method involves positioning a base core on a suitable surface and building up or stacking separate mold elements to shape such casting features as the sides, ends, water jacket, cam openings, and crankcase. The bore liners are positioned on barrel core features such that the liners become embedded in the casting after the metal is poured into the mold. Additional cores may be present as well depending on the engine design. Various designs for the barrel cores are used in the industry. These include individual barrel cores, “V” pairs of barrel cores, barrel-slab cores, and integral barrel crankcase cores. The barrel-slab and integral barrel crankcase designs are often preferred because they provide more accurate positioning of the liners within the mold assembly.
The engine block casting must be machined in a manner to ensure, among other things, that the cylinder bores (formed from the bore liners positioned on the barrel features of the barrel cores) have uniform bore liner wall thickness, and that other critical block features are accurately machined. This requires the liners to be accurately positioned relative to one another within the casting. The ease and consistency with which the bore liners are brought into the desired final position during the mold assembly process is an important consideration.
In barrel slab cores, the bore liners are positioned on the barrel core features by slidingly placing the bore liners on the barrel core features. Alternatively, the liners may be placed into the core tooling and the core sand blown into the liners to form the barrel core feature. Prior to casting, the barrel-slab cores are inverted for assembly into the mold package. Undesirable movement of the bore liners relative to the slab core may occur while the assembly is inverted.
One attempt to resolve the issues described above is disclosed in U.S. Pat. No. 5,365,997. In the '997 patent, an internal diameter chamfer is incorporated into the cylinder bore liner design to militate against undesirable displacement of the cylinder bore liner. Another attempt to resolve the issues described above is disclosed in U.S. Pat. No. 5,730,200. In the '200 patent, an expanding mandrel is used inside of a hollow barrel core to secure the cylinder bore liner to the barrel core during assembly of the mold package.
It would be desirable to produce a mold assembly device which secures a cast-in-place cylinder bore liner for use in sand casting of engine cylinder blocks during assembly of a mold package, wherein the mold assembly device militates against undesirable movement of the bore liner during assembly of the mold package.